Electrographic printer using fluidic charge dissipation

Abstract

Electrographic printing apparatus for producing a toner image on paper includes a dryer adapted to dry a selected region of the paper to a moisture content not to exceed that of the paper equilibrated to 20% RH. A liquid-deposition unit wets selected portions of the selected region of the paper within 15 seconds after the completion of drying to provide a latent fluid image corresponding to the wetted portions of the paper. A dry area is thereby defined in the selected region outside the latent fluid image. A charging member charges the paper so that the paper in the dry area has a selected potential. A development station deposits charged dry toner in the selected region, the toner having charge of the same sign as the selected potential, so that the toner adheres to paper in the area of the latent fluid image.

1 . Electrographic printing apparatus for producing a toner image on paper, the apparatus comprising:
 a dryer adapted to dry a selected region of the paper to a moisture content not to exceed that of the paper equilibrated to 20% RH;   a liquid-deposition unit adapted to wet selected portions of the selected region of the paper within  15  seconds after the completion of drying to provide a latent fluid image corresponding to the wetted portions of the paper, whereby a dry area is defined in the selected region outside the latent fluid image;   a charging member for charging the paper so that the paper in the dry area has a selected potential; and   a development station for depositing charged dry toner in the selected region, the toner having charge of the same sign as the selected potential, so that the toner adheres to paper in the area of the latent fluid image.   
     
     
         2 . The apparatus according to  claim 1 , wherein the toner includes particles having diameters less than 200 μm. 
     
     
         3 . The apparatus according to  claim 1 , wherein the toner includes particles having diameters between 4 μm and 25 μm. 
     
     
         4 . The apparatus according to  claim 1 , wherein the toner does not include colorant. 
     
     
         5 . The apparatus according to  claim 1 , wherein the toner includes toner particles and does not include particulate addenda having diameters <1 μm on a surface of the toner particles. 
     
     
         6 . The apparatus according to  claim 5 , wherein the toner particles have diameters between 4 μm and 12 μm. 
     
     
         7 . The apparatus according to  claim 1 , wherein the charging member includes two electrodes arranged on opposite sides of the paper path and adapted to selectively charge the selected region of the paper between them. 
     
     
         8 . The apparatus according to  claim 1 , wherein the development station includes a biasable toning member and a biasable area electrode arranged on opposite sides of the selected region of the paper.